chemistry yoww

2. Hollowcathode lamps
Electrodeless
discharge
lamps
• Improve: lamps can be operated using short
duration pulses (maintain the mean lamp
current at low level)
• Pulses lamps provide an increase in peak
intensity & reduction of the total signal
observation time
• Useful sources of atomic line spectra &
provide radiant intensities that are usually
1 or 2 orders of magnitude greater than
normal HCL
• The lamp doesn’t contain an electron but
energized by an intense field of radio
frequency or microwave radiation

3. Xenon arc
lamps
• Producing stable & intense continuum source
(high pressure XAL)
• Lamp producing intense radiation by the passage
of current through an atmosphere of xenon
• Advantage: can be readily employed for multi
element analysis
Laser
sources
• Important sources (analytical) because high
intensity, narrow bandwidths & coherent nature
of their outputs
• Laser-induced fluorescence offers a very sensitive
& selective
• Laser excitation allows non-resonance transition
lines to be used for many elements
Mercury
arc lamps
• Type of vapor-discharge lamp that forms
simple, robust sources of line spectra

5. Flame
• Convenient
& widely
used
• Large
sample
requirement
Electrothermal
• Operated at
high
temperature
& atoms are
contained in
inert
atmosphere

6. Cold-vapor technique
for mercury
• Measuring
mercury without
the additional
thermal energy
supplied
Inductively coupled
plasma (ICP)
• High cost
compared with
flame &
electrothermal
• Plasmas have
better
vaporization &
atomization
efficiency

7. 
Requirements for wavelength selection depend
on the light source employed
Conventio
nal line
sources or
laser
excitation
Lowdispersion
monochromato
rs or nondispersive
systems can be
used
Photomulti
plier tube
•Highly
sensitive
•Fast
response
times